CVE-2026-70399 — httpd does not enforce the documented default max_clients connection limit

Affected: Erlang OTP

Allocation of Resources Without Limits or Throttling vulnerability in Erlang/OTP inets httpd allows an unauthenticated remote attacker to cause denial of service by opening and holding open a large number of connections. The max_clients option is documented to default to 150, and the inets hardening guide presents that limit as the first layer of denial-of-service defence, but a server that does not set it explicitly accepts an unlimited number of simultaneous connections. Establishing the connections is sufficient; no valid request and no authentication are required.

The accept gate in httpd_manager:handle_new_connection/4 reads the option with httpd_util:lookup/2, which returns undefined when the key is absent, rather than the three-argument form carrying the 150 default that the neighbouring get_ustate/2 uses. Erlang term ordering places every integer before every atom, so the Count =< Max guard holds for any connection count and the server never returns {reject, busy}. Each accepted connection occupies a worker process and a socket for as long as it is held, driving the node towards process, memory and file descriptor exhaustion. Servers that set max_clients explicitly are unaffected, because a configured value is applied as intended.

This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2.

USN-8827-1 — erlang vulnerabilities

Affected: Ubuntu:Pro:14.04:LTS: erlang, Ubuntu:Pro:16.04:LTS: erlang, Ubuntu:Pro:18.04:LTS: erlang, Ubuntu:Pro:20.04:LTS: erlang, Ubuntu:22.04:LTS: erlang, Ubuntu:24.04:LTS: erlang, Ubuntu:26.04:LTS: erlang

It was discovered that the Erlang Port Mapper Daemon did not properly handle slow connections. A remote attacker could possibly use this issue to cause a denial of service. (CVE-2026-42792)

It was discovered that Erlang incorrectly handled certain external term format data, leading to heap corruption. An attacker could possibly use this issue to cause Erlang to crash, resulting in a denial of service. This issue only affected Ubuntu 24.04 LTS and Ubuntu 26.04 LTS. (CVE-2026-55737)

It was discovered that Erlang incorrectly handled invalid external term format data. An attacker could possibly use this issue to cause Erlang to crash, resulting in a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-54890)

It was discovered that Erlang incorrectly handled certain packet lengths, leading to a buffer overflow. A remote attacker could possibly use this issue to cause Erlang to crash or execute arbitrary code. (CVE-2026-75538)

It was discovered that the Erlang Megaco flex scanner incorrectly handled certain input, leading to a buffer overflow. A remote attacker could possibly use this issue to cause Erlang to crash or execute arbitrary code. (CVE-2026-59250)

It was discovered that Erlang TLS clients incorrectly accepted cipher suites that they had not offered. A remote attacker could possibly use this issue to intercept and modify TLS communications. (CVE-2026-55953)

It was discovered that Erlang incorrectly handled certain certificate chains. A remote att…

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CVE-2026-70399 — httpd does not enforce the documented default max_clients connection limit

USN-8827-1 — erlang vulnerabilities